Refactor mkFlag / shouldUsePkg into the nixpkgs libraries

lib/customisation.nix

@@ -158,4 +158,27 @@ rec {
       drv' = (lib.head outputsList).value;
     in lib.deepSeq drv' drv';
 
+
+  /* Tests whether a derivation can be used by the current platform
+     Returns the derivation if true, otherwise null. */
+  shouldUsePkgSystem = system: pkg_: let pkg = (builtins.tryEval pkg_).value;
+    in if lib.any (x: x == system) (pkg.meta.platforms or [])
+      then pkg
+      else null;
+
+  /* Returns a configure flag string in an autotools format
+     trueStr: Prepended when cond is true
+     falseStr: Prepended when cond is false
+     cond: The condition for the prepended string type and value
+     name: The flag name
+     val: The value of the flag only set when cond is true */
+  mkFlag = trueStr: falseStr: cond: name: val:
+    if cond == null then null else
+      "--${if cond != false then trueStr else falseStr}${name}"
+      + "${if val != null && cond != false then "=${val}" else ""}";
+
+  /* Flag setting helpers for autotools like packages */
+  mkEnable = mkFlag "enable-" "disable-";
+  mkWith = mkFlag "with-" "without-";
+  mkOther = mkFlag "" "" true;
 }

pkgs/applications/virtualization/qemu/default.nix

@@ -27,65 +27,60 @@
 , type ? ""
 }:
 
+with stdenv;
 with stdenv.lib;
 let
   n = "qemu-2.3.0";
 
-  mkFlag = trueStr: falseStr: cond: name: val:
-    if cond == null then null else
-      "--${if cond != false then trueStr else falseStr}${name}${if val != null && cond != false then "=${val}" else ""}";
-  mkEnable = mkFlag "enable-" "disable-";
-  mkWith = mkFlag "with-" "without-";
-  mkOther = mkFlag "" "" true;
+  isKvmOnly = type == "kvm-only";
+  isNix = type == "nix";
 
-  shouldUsePkg = pkg: if pkg != null && stdenv.lib.any (x: x == stdenv.system) pkg.meta.platforms then pkg else null;
-
-  optSDL2 = if type == "nix" then null else shouldUsePkg SDL2;
-  optGtk = if type == "nix" then null else shouldUsePkg gtk;
-  optLibcap = if type == "nix" then null else shouldUsePkg libcap;
-  optAttr = if type == "nix" then null else shouldUsePkg attr;
-  optGnutls = if type == "nix" then null else shouldUsePkg gnutls;
-  optCyrus_sasl = if type == "nix" then null else shouldUsePkg cyrus_sasl;
-  optLibjpeg = if type == "nix" then null else shouldUsePkg libjpeg;
-  optLibpng = if type == "nix" then null else shouldUsePkg libpng;
-  optNcurses = if type == "nix" then null else shouldUsePkg ncurses;
-  optCurl = if type == "nix" then null else shouldUsePkg curl;
-  optBluez = if type == "nix" then null else shouldUsePkg bluez;
-  optLibibverbs = if type == "nix" then null else shouldUsePkg libibverbs;
-  optLibrdmacm = if type == "nix" then null else shouldUsePkg librdmacm;
-  optLibuuid = if type == "nix" then null else shouldUsePkg libuuid;
-  optVde2 = if type == "nix" then null else shouldUsePkg vde2;
+  optSDL2 = if isNix then null else shouldUsePkg SDL2;
+  optGtk = if isNix then null else shouldUsePkg gtk;
+  optLibcap = if isNix then null else shouldUsePkg libcap;
+  optAttr = if isNix then null else shouldUsePkg attr;
+  optGnutls = if isNix then null else shouldUsePkg gnutls;
+  optCyrus_sasl = if isNix then null else shouldUsePkg cyrus_sasl;
+  optLibjpeg = if isNix then null else shouldUsePkg libjpeg;
+  optLibpng = if isNix then null else shouldUsePkg libpng;
+  optNcurses = if isNix then null else shouldUsePkg ncurses;
+  optCurl = if isNix then null else shouldUsePkg curl;
+  optBluez = if isNix then null else shouldUsePkg bluez;
+  optLibibverbs = if isNix then null else shouldUsePkg libibverbs;
+  optLibrdmacm = if isNix then null else shouldUsePkg librdmacm;
+  optLibuuid = if isNix then null else shouldUsePkg libuuid;
+  optVde2 = if isNix then null else shouldUsePkg vde2;
   optLibaio = shouldUsePkg libaio;
   optLibcap_ng = shouldUsePkg libcap_ng;
-  optSpice = if type == "nix" then null else shouldUsePkg spice;
-  optSpice_protocol = if type == "nix" then null else shouldUsePkg spice_protocol;
-  optLibceph = if type == "nix" then null else shouldUsePkg libceph;
-  optLibxfs = if type == "nix" then null else shouldUsePkg libxfs;
-  optNss = if type == "nix" then null else shouldUsePkg nss;
-  optNspr = if type == "nix" then null else shouldUsePkg nspr;
-  optLibusb = if type == "nix" then null else shouldUsePkg libusb;
-  optUsbredir = if type == "nix" then null else shouldUsePkg usbredir;
-  optMesa = if type == "nix" then null else shouldUsePkg mesa;
-  optLzo = if type == "nix" then null else shouldUsePkg lzo;
-  optSnappy = if type == "nix" then null else shouldUsePkg snappy;
-  optBzip2 = if type == "nix" then null else shouldUsePkg bzip2;
-  optLibseccomp = if type == "nix" then null else shouldUsePkg libseccomp;
-  optGlusterfs = if type == "nix" then null else shouldUsePkg glusterfs;
-  optLibssh2 = if type == "nix" then null else shouldUsePkg libssh2;
-  optNumactl = if type == "nix" then null else shouldUsePkg numactl;
+  optSpice = if isNix then null else shouldUsePkg spice;
+  optSpice_protocol = if isNix then null else shouldUsePkg spice_protocol;
+  optLibceph = if isNix then null else shouldUsePkg libceph;
+  optLibxfs = if isNix then null else shouldUsePkg libxfs;
+  optNss = if isNix then null else shouldUsePkg nss;
+  optNspr = if isNix then null else shouldUsePkg nspr;
+  optLibusb = if isNix then null else shouldUsePkg libusb;
+  optUsbredir = if isNix then null else shouldUsePkg usbredir;
+  optMesa = if isNix then null else shouldUsePkg mesa;
+  optLzo = if isNix then null else shouldUsePkg lzo;
+  optSnappy = if isNix then null else shouldUsePkg snappy;
+  optBzip2 = if isNix then null else shouldUsePkg bzip2;
+  optLibseccomp = if isNix then null else shouldUsePkg libseccomp;
+  optGlusterfs = if isNix then null else shouldUsePkg glusterfs;
+  optLibssh2 = if isNix then null else shouldUsePkg libssh2;
+  optNumactl = if isNix then null else shouldUsePkg numactl;
 
   hasSDLAbi = if optSDL2 != null then true else null;
 
   hasVirtfs = stdenv.isLinux && optLibcap != null && optAttr != null;
 
-  hasVnc = type != "nix";
+  hasVnc = !isNix;
   hasVncTls = hasVnc && optGnutls != null;
   hasVncSasl = hasVnc && optCyrus_sasl != null;
   hasVncJpeg = hasVnc && optLibjpeg != null;
   hasVncPng = hasVnc && optLibpng != null;
   hasVncWs = hasVnc && optGnutls != null;
 
-  hasFdt = type != "nix";
+  hasFdt = !isNix;
 
   hasRdma = optLibibverbs != null && optLibrdmacm != null;
 
@@ -95,8 +90,8 @@ let
 
   hasNss = optNss != null && optNspr != null;
 
-  optLibpulseaudio = if type == "nix" then null else shouldUsePkg libpulseaudio;
-  optAlsaLib = if type == "nix" then null else shouldUsePkg alsaLib;
+  optLibpulseaudio = if isNix then null else shouldUsePkg libpulseaudio;
+  optAlsaLib = if isNix then null else shouldUsePkg alsaLib;
   audio = concatStringsSep "," (
        optional (optSDL2 != null) "sdl"
     ++ optional (optLibpulseaudio != null) "pa"
@@ -179,9 +174,9 @@ stdenv.mkDerivation rec {
     (mkEnable (optBluez != null)      "bluez"               null)
     (mkEnable stdenv.isLinux          "kvm"                 null)
     (mkEnable hasRdma                 "rdma"                null)
-    (mkEnable (type != "nix")         "system"              null)
-    (mkEnable (type != "kvm-only")    "user"                null)
-    (mkEnable (type != "kvm-only")    "guest-base"          null)
+    (mkEnable (!isNix)                "system"              null)
+    (mkEnable (!isKvmOnly)            "user"                null)
+    (mkEnable (!isKvmOnly)            "guest-base"          null)
     (mkEnable true                    "pie"                 null)
     (mkEnable (optLibuuid != null)    "uuid"                null)
     (mkEnable (optVde2 != null)       "vde"                 null)
@@ -189,7 +184,7 @@ stdenv.mkDerivation rec {
     (mkEnable hasLinuxAio             "linux-aio"           null)
     (mkEnable (optLibcap_ng != null)  "cap-ng"              null)
     (mkEnable (optAttr != null)       "attr"                null)
-    (mkEnable (type != "nix")         "docs"                null)
+    (mkEnable (!isNix)                "docs"                null)
     (mkEnable stdenv.isLinux          "vhost-net"           null)
     (mkEnable hasSpice                "spice"               null)
     (mkEnable (optLibceph != null)    "rbd"                 null)
@@ -212,7 +207,7 @@ stdenv.mkDerivation rec {
     (mkEnable (optLibuuid != null)    "vhdx"                null)
     (mkEnable (optGnutls != null)     "quorum"              null)
     (mkEnable (optNumactl != null)    "numa"                null)
-  ] ++ optionals (type == "kvm-only") [
+  ] ++ optionals isKvmOnly [
     (mkOther                          "target-list"         targetList)
   ];
 
@@ -235,6 +230,6 @@ stdenv.mkDerivation rec {
     description = "A generic and open source machine emulator and virtualizer";
     license = licenses.gpl2Plus;
     maintainers = with maintainers; [ viric shlevy eelco wkennington ];
-    platforms = if type == "kvm-only" then platforms.linux else platforms.all;
+    platforms = if isKvmOnly then platforms.linux else platforms.all;
   };
 }

pkgs/development/libraries/kerberos/heimdal.nix

@@ -8,16 +8,9 @@
 #, sqlite, db, ncurses, openssl, cyrus_sasl
 }:
 
+with stdenv;
+with stdenv.lib;
 let
-  mkFlag = trueStr: falseStr: cond: name: val:
-    if cond == null then null else
-      "--${if cond != false then trueStr else falseStr}${name}${if val != null && cond != false then "=${val}" else ""}";
-  mkEnable = mkFlag "enable-" "disable-";
-  mkWith = mkFlag "with-" "without-";
-  mkOther = mkFlag "" "" true;
-
-  shouldUsePkg = pkg: if pkg != null && stdenv.lib.any (x: x == stdenv.system) pkg.meta.platforms then pkg else null;
-
   optOpenldap = shouldUsePkg openldap;
   optLibcap_ng = shouldUsePkg libcap_ng;
   optSqlite = shouldUsePkg sqlite;
@@ -97,7 +90,7 @@ stdenv.mkDerivation rec {
     rmdir $out/libexec
   '';
 
-  meta = with stdenv.lib; {
+  meta = {
     description = "an implementation of Kerberos 5 (and some more stuff) largely written in Sweden";
     license = licenses.bsd3;
     platforms = platforms.linux;

pkgs/development/libraries/libgcrypt/default.nix

@@ -5,16 +5,9 @@
 , libcap ? null, pth ? null
 }:
 
+with stdenv;
+with stdenv.lib;
 let
-  mkFlag = trueStr: falseStr: cond: name: val:
-    if cond == null then null else
-      "--${if cond != false then trueStr else falseStr}${name}${if val != null && cond != false then "=${val}" else ""}";
-  mkEnable = mkFlag "enable-" "disable-";
-  mkWith = mkFlag "with-" "without-";
-  mkOther = mkFlag "" "" true;
-
-  shouldUsePkg = pkg: if pkg != null && stdenv.lib.any (x: x == stdenv.system) pkg.meta.platforms then pkg else null;
-
   optLibcap = shouldUsePkg libcap;
   #optPth = shouldUsePkg pth;
   optPth = null; # Broken as of 1.6.3
@@ -38,13 +31,13 @@ stdenv.mkDerivation rec {
   # Also make sure includes are fixed for callers who don't use libgpgcrypt-config
   postInstall = ''
     sed -i 's,#include <gpg-error.h>,#include "${libgpgerror}/include/gpg-error.h",g' $out/include/gcrypt.h
-  '' + stdenv.lib.optionalString (!stdenv.isDarwin && optLibcap != null) ''
+  '' + optionalString (!stdenv.isDarwin && optLibcap != null) ''
     sed -i 's,\(-lcap\),-L${optLibcap}/lib \1,' $out/lib/libgcrypt.la
   '';
 
   doCheck = true;
 
-  meta = with stdenv.lib; {
+  meta = {
     homepage = https://www.gnu.org/software/libgcrypt/;
     description = "General-pupose cryptographic library";
     license = licenses.lgpl2Plus;

pkgs/development/libraries/libmicrohttpd/default.nix

@@ -5,16 +5,8 @@
 , openssl ? null, zlib ? null, libgcrypt ? null, gnutls ? null
 }:
 
+with stdenv;
 let
-  mkFlag = trueStr: falseStr: cond: name: val:
-    if cond == null then null else
-      "--${if cond != false then trueStr else falseStr}${name}${if val != null && cond != false then "=${val}" else ""}";
-  mkEnable = mkFlag "enable-" "disable-";
-  mkWith = mkFlag "with-" "without-";
-  mkOther = mkFlag "" "" true;
-
-  shouldUsePkg = pkg: if pkg != null && stdenv.lib.any (x: x == stdenv.system) pkg.meta.platforms then pkg else null;
-
   optOpenssl = shouldUsePkg openssl;
   optZlib = shouldUsePkg zlib;
   hasSpdy = optOpenssl != null && optZlib != null;

pkgs/development/libraries/libssh/default.nix

@@ -7,9 +7,8 @@
 , openssl ? null, libgcrypt ? null
 }:
 
+with stdenv;
 let
-  shouldUsePkg = pkg: if pkg != null && stdenv.lib.any (x: x == stdenv.system) pkg.meta.platforms then pkg else null;
-
   # Prefer openssl
   cryptoStr = if shouldUsePkg openssl != null then "openssl"
     else if shouldUsePkg libgcrypt != null then "libgcrypt"

pkgs/development/libraries/libssh2/default.nix

@@ -7,16 +7,8 @@
 , openssl ? null, libgcrypt ? null
 }:
 
+with stdenv;
 let
-  mkFlag = trueStr: falseStr: cond: name: val:
-    if cond == null then null else
-      "--${if cond != false then trueStr else falseStr}${name}${if val != null && cond != false then "=${val}" else ""}";
-  mkEnable = mkFlag "enable-" "disable-";
-  mkWith = mkFlag "with-" "without-";
-  mkOther = mkFlag "" "" true;
-
-  shouldUsePkg = pkg: if pkg != null && stdenv.lib.any (x: x == stdenv.system) pkg.meta.platforms then pkg else null;
-
   # Prefer openssl
   cryptoStr = if shouldUsePkg openssl != null then "openssl"
     else if shouldUsePkg libgcrypt != null then "libgcrypt"

pkgs/development/libraries/libxml2/default.nix

@@ -6,16 +6,8 @@
 
 #TODO: share most stuff between python and non-python builds, perhaps via multiple-output
 
+with stdenv;
 let
-  mkFlag = trueStr: falseStr: cond: name: val:
-    if cond == null then null else
-      "--${if cond != false then trueStr else falseStr}${name}${if val != null && cond != false then "=${val}" else ""}";
-  mkEnable = mkFlag "enable-" "disable-";
-  mkWith = mkFlag "with-" "without-";
-  mkOther = mkFlag "" "" true;
-
-  shouldUsePkg = pkg: if pkg != null && stdenv.lib.any (x: x == stdenv.system) pkg.meta.platforms then pkg else null;
-
   optIcu = shouldUsePkg icu;
   optPython = shouldUsePkg python;
   optReadline = shouldUsePkg readline;
@@ -25,6 +17,7 @@ let
   sitePackages = if optPython == null then null else
     "\${out}/lib/${python.libPrefix}/site-packages";
 in
+with stdenv.lib;
 stdenv.mkDerivation rec {
   name = "libxml2-${version}";
   version = "2.9.2";

pkgs/development/libraries/ncurses/default.nix

@@ -8,23 +8,11 @@
 , unicode ? true
 }:
 
+with stdenv.lib;
 let
-  mkFlag = trueStr: falseStr: cond: name: val:
-    if cond == null then null else
-      "--${if cond != false then trueStr else falseStr}${name}${if val != null && cond != false then "=${val}" else ""}";
-  mkEnable = mkFlag "enable-" "disable-";
-  mkWith = mkFlag "with-" "without-";
-  mkOther = mkFlag "" "" true;
-
-  shouldUsePkg = pkg_: let
-    pkg = (builtins.tryEval pkg_).value;
-  in if stdenv.lib.any (x: x == stdenv.system) (pkg.meta.platforms or [])
-    then pkg
-    else null;
-
   buildShared = !stdenv.isDarwin;
 
-  optGpm = shouldUsePkg gpm;
+  optGpm = stdenv.shouldUsePkg gpm;
 in
 stdenv.mkDerivation rec {
   name = "ncurses-5.9";
@@ -119,7 +107,7 @@ stdenv.mkDerivation rec {
     echo "INPUT(-lncurses)" > $out/lib/libcurses.so
   '';
 
-  meta = with stdenv.lib; {
+  meta = {
     description = "Free software emulation of curses in SVR4 and more";
 
     longDescription = ''

pkgs/development/libraries/nghttp2/default.nix

@@ -8,16 +8,9 @@
 , prefix ? ""
 }:
 
+with stdenv;
+with stdenv.lib;
 let
-  mkFlag = trueStr: falseStr: cond: name: val:
-    if cond == null then null else
-      "--${if cond != false then trueStr else falseStr}${name}${if val != null && cond != false then "=${val}" else ""}";
-  mkEnable = mkFlag "enable-" "disable-";
-  mkWith = mkFlag "with-" "without-";
-  mkOther = mkFlag "" "" true;
-
-  shouldUsePkg = pkg: if pkg != null && stdenv.lib.any (x: x == stdenv.system) pkg.meta.platforms then pkg else null;
-
   isLib = prefix == "lib";
 
   optOpenssl = if isLib then null else shouldUsePkg openssl;
@@ -50,7 +43,7 @@ stdenv.mkDerivation rec {
 
   nativeBuildInputs = [ pkgconfig ];
   buildInputs = [ optJansson optBoost optLibxml2 optJemalloc ]
-    ++ stdenv.lib.optionals hasApp [ optOpenssl optLibev optZlib ];
+    ++ optionals hasApp [ optOpenssl optLibev optZlib ];
 
   configureFlags = [
     (mkEnable false                 "werror"          null)
@@ -68,7 +61,7 @@ stdenv.mkDerivation rec {
     (mkWith   false                 "cython"          null)
   ];
 
-  meta = with stdenv.lib; {
+  meta = {
     homepage = http://nghttp2.org/;
     description = "an implementation of HTTP/2 in C";
     license = licenses.mit;

pkgs/development/libraries/wiredtiger/default.nix

@@ -5,17 +5,8 @@
 , gperftools ? null, leveldb ? null
 }:
 
-with stdenv.lib;
+with stdenv;
 let
-  mkFlag = trueStr: falseStr: cond: name: val:
-    if cond == null then null else
-      "--${if cond != false then trueStr else falseStr}${name}${if val != null && cond != false then "=${val}" else ""}";
-  mkEnable = mkFlag "enable-" "disable-";
-  mkWith = mkFlag "with-" "without-";
-  mkOther = mkFlag "" "" true;
-
-  shouldUsePkg = pkg: if pkg != null && any (x: x == stdenv.system) pkg.meta.platforms then pkg else null;
-
   optLz4 = shouldUsePkg lz4;
   optSnappy = shouldUsePkg snappy;
   optZlib = shouldUsePkg zlib;
@@ -24,6 +15,7 @@ let
   optGperftools = shouldUsePkg gperftools;
   optLeveldb = shouldUsePkg leveldb;
 in
+with stdenv.lib;
 stdenv.mkDerivation rec {
   name = "wiredtiger-${version}";
   version = "2.6.0";

pkgs/misc/jackaudio/default.nix

@@ -9,10 +9,9 @@
 , prefix ? ""
 }:
 
+with stdenv;
 with stdenv.lib;
 let
-  shouldUsePkg = pkg: if pkg != null && stdenv.lib.any (x: x == stdenv.system) pkg.meta.platforms then pkg else null;
-
   libOnly = prefix == "lib";
 
   optDbus = shouldUsePkg dbus;

pkgs/misc/jackaudio/jack1.nix

@@ -4,9 +4,8 @@
 , alsaLib ? null, db ? null, libuuid ? null, libffado ? null, celt ? null
 }:
 
+with stdenv;
 let
-  shouldUsePkg = pkg: if pkg != null && stdenv.lib.any (x: x == stdenv.system) pkg.meta.platforms then pkg else null;
-
   optAlsaLib = shouldUsePkg alsaLib;
   optDb = shouldUsePkg db;
   optLibuuid = shouldUsePkg libuuid;

pkgs/os-specific/linux/ffado/default.nix

@@ -9,10 +9,8 @@
 , prefix ? ""
 }:
 
+with stdenv;
 let
-
-  shouldUsePkg = pkg: if pkg != null && stdenv.lib.any (x: x == stdenv.system) pkg.meta.platforms then pkg else null;
-
   libOnly = prefix == "lib";
 
   optLibjack2 = shouldUsePkg libjack2;

pkgs/servers/pulseaudio/default.nix

@@ -15,16 +15,8 @@
 , prefix ? ""
 }:
 
+with stdenv;
 let
-  mkFlag = trueStr: falseStr: cond: name: val:
-    if cond == null then null else
-      "--${if cond != false then trueStr else falseStr}${name}${if val != null && cond != false then "=${val}" else ""}";
-  mkEnable = mkFlag "enable-" "disable-";
-  mkWith = mkFlag "with-" "without-";
-  mkOther = mkFlag "" "" true;
-
-  shouldUsePkg = pkg: if pkg != null && stdenv.lib.any (x: x == stdenv.system) pkg.meta.platforms then pkg else null;
-
   libOnly = prefix == "lib";
 
   hasXlibs = xlibs != null;
@@ -66,6 +58,7 @@ let
     simple = null;
   }.${databaseName};
 in
+with stdenv.lib;
 stdenv.mkDerivation rec {
   name = "${prefix}pulseaudio-${version}";
   version = "6.0";
@@ -84,9 +77,9 @@ stdenv.mkDerivation rec {
     optLibcap valgrind optOss optCoreaudio optAlsaLib optEsound optGlib
     optGtk3 optGconf optAvahi optLibjack2 optLibasyncns optLirc optDbus optUdev
     optOpenssl optFftw optSpeexdsp optSystemd optWebrtc-audio-processing
-  ] ++ stdenv.lib.optionals hasXlibs (with xlibs; [
+  ] ++ optionals hasXlibs (with xlibs; [
       libX11 libxcb libICE libSM libXtst xextproto libXi
-    ]) ++ stdenv.lib.optionals (optBluez5 != null) [ optBluez5 optSbc ];
+    ]) ++ optionals (optBluez5 != null) [ optBluez5 optSbc ];
 
   preConfigure = ''
     # Performs and autoreconf
@@ -162,7 +155,7 @@ stdenv.mkDerivation rec {
   # the alternative is to copy the files from /usr/include to src, but there are
   # probably a large number of files that would need to be copied (I stopped
   # after the seventh)
-  NIX_CFLAGS_COMPILE = stdenv.lib.optionalString stdenv.isDarwin
+  NIX_CFLAGS_COMPILE = optionalString stdenv.isDarwin
     "-I/usr/include";
 
   installFlags = [
@@ -170,11 +163,11 @@ stdenv.mkDerivation rec {
     "pulseconfdir=$(out)/etc/pulse"
   ];
 
-  postInstall = stdenv.lib.optionalString libOnly ''
+  postInstall = optionalString libOnly ''
     rm -rf $out/{bin,share,etc,lib/{pulse-*,systemd}}
   '';
 
-  meta = with stdenv.lib; {
+  meta = {
     description = "Sound server for POSIX and Win32 systems";
     homepage    = http://www.pulseaudio.org/;
     # Note: Practically, the server is under the GPL due to the

pkgs/servers/shishi/default.nix

@@ -5,16 +5,8 @@
 , pam ? null, libidn ? null, gnutls ? null
 }:
 
+with stdenv;
 let
-  mkFlag = trueStr: falseStr: cond: name: val:
-    if cond == null then null else
-      "--${if cond != false then trueStr else falseStr}${name}${if val != null && cond != false then "=${val}" else ""}";
-  mkEnable = mkFlag "enable-" "disable-";
-  mkWith = mkFlag "with-" "without-";
-  mkOther = mkFlag "" "" true;
-
-  shouldUsePkg = pkg: if pkg != null && stdenv.lib.any (x: x == stdenv.system) pkg.meta.platforms then pkg else null;
-
   optPam = shouldUsePkg pam;
   optLibidn = shouldUsePkg libidn;
   optGnutls = shouldUsePkg gnutls;

pkgs/stdenv/generic/default.nix

@@ -229,6 +229,8 @@ let
            || system == "armv7l-linux";
       isBigEndian = system == "powerpc-linux";
 
+      shouldUsePkg = lib.shouldUsePkgSystem system;
+
       # Whether we should run paxctl to pax-mark binaries.
       needsPax = isLinux;
 

pkgs/tools/networking/curl/default.nix

@@ -8,19 +8,12 @@
 , suffix ? ""
 }:
 
+with stdenv;
+with stdenv.lib;
 let
-  mkFlag = trueStr: falseStr: cond: name: val:
-    if cond == null then null else
-      "--${if cond != false then trueStr else falseStr}${name}${if val != null && cond != false then "=${val}" else ""}";
-  mkEnable = mkFlag "enable-" "disable-";
-  mkWith = mkFlag "with-" "without-";
-  mkOther = mkFlag "" "" true;
-
-  shouldUsePkg = pkg: if pkg != null && stdenv.lib.any (x: x == stdenv.system) pkg.meta.platforms then pkg else null;
-
   isLight = suffix == "light";
   isFull = suffix == "full";
-  nameSuffix = stdenv.lib.optionalString (suffix != "") "-${suffix}";
+  nameSuffix = optionalString (suffix != "") "-${suffix}";
 
   # Normal Depedencies
   optZlib = if isLight then null else shouldUsePkg zlib;
@@ -35,7 +28,6 @@ let
   optOpenldap = if !isFull then null else shouldUsePkg openldap;
   optLibidn = if !isFull then null else shouldUsePkg libidn;
 in
-with stdenv.lib;
 stdenv.mkDerivation rec {
   name = "curl${nameSuffix}-${version}";
   version = "7.42.1";